Damascene is an interconnection fabrication process in which grooves are formed in an insulating layer and filled with metal to form conductive lines (interconnects). Dual damascene is a multi-level interconnection process in which, in addition to forming the grooves of single damascene, conductive contact (or via) openings are also formed. In the standard dual damascene process, a single or composite insulating layer (typically oxide) is coated with a photoresist which is exposed through a first mask with the image pattern of the contact openings and the pattern is etched. A second mask pattern is then formed with the interconnect pattern. The insulating layer is then etched a second time. Finally, a conductive material such as aluminum or copper is deposited into the grooves and contact openings formed in the insulating layer. Additionally, a Ti or TiN layer may be used as a barrier layer or to act as an adhesion layer.
However, as the level of integration increases, and as the dual damascene structures become smaller, the Ti or TiN layer is difficult to deposit uniformly into deep sub-micron contact openings.
What is needed is a new process for forming a dual damascene contact and interconnect.